1. Field of the Invention
The invention relates generally to methods of sizing metal sleeves, and particularly relates to a method of sizing metal sleeves using a magnetic field.
2. Discussion of the Related Art
The process of sizing metal sleeves generally includes expanding the metal sleeve, or at least a portion thereof, to a desired finished shape. Several methods of sizing metal sleeves are known in the art. One known method provides for the insertion of a mandrel into the metal sleeve. An inner surface of the metal sleeve is generally coated with a lubricant and the mandrel contacts the inner surface to expand the metal sleeve to a desired size. Another method, known as hydroforming, uses hydraulic pressure to expand the metal sleeve. Fluid is passed through the metal sleeve and contacts the inner surface. The resulting pressure is controlled to expand the metal sleeve to a desired size.
Another known method of metal forming uses a magnetic field to exert pressure on the sleeve. This method generally requires the use of sleeves composed of electrically conductive material. The conductive sleeves are placed in a split die with a magnetic coil. The magnetic coil generates a magnetic field which induces current in the conductive sleeve, thereby creating an opposing magnetic field. The net magnetic force between the two opposing magnetic fields exerts substantial pressure on the sleeve to expand the sleeve against an inner surface of the die. This process is disclosed in U.S. Pat. No. 2,976,907, which is incorporated herein by reference.
Several applications require the sized metal sleeves to have precise and uniform dimensions, and highly polished outer surfaces. For example, components used in xerographic apparatus, such as photoreceptor substrates, must be uniformly sized and have highly polished outer surfaces to ensure that a toner powder image formed on the photoreceptor substrate is accurately transferred to a copy sheet to clearly depict an image of the original document.
The aforementioned methods cannot consistently produce sized sleeves having uniform dimensions and highly polished outer surfaces. The hydroforming and mandrel methods, which require physical contact with the inner surface of the sleeve, do not consistently produce sized sleeves having precise and uniform dimensions. Additionally, these methods may also damage the inner surface of the sleeve due to the requirement of physical contact. The method of sizing using a split die and magnetic coil can generally produce sized sleeves having more precise and uniform dimensions than those requiring physical contact with the sleeve. However, the outer surfaces of the sized sleeves are not always highly polished since surface deformities caused by the joint of the split die may occur. Additionally, air pockets between the inner surface of the split die and the outer surface of the metal sleeve during the sizing process may cause the metal sleeve to become deformed. As a result, these processes usually require additional machining of the outer surface of the metal sleeve to ensure that the outer surface is precise, uniform, and highly polished.